The present invention relates to a surface treatment process for fabricating a panel of an organic light emitting device (OLED), especially associates to a surface treatment process for the isolating walls on a panel of an OLED.
The latest OLED dominated a focus of developing flat panel display (FPD) technology in recent years. Compared with other FPDs such as LCDs (liquid crystal displays) and FEDs (Field emission displays), OLED display panels have many distinguished advantages such as light weight, high contrast, fast response speed, low power consumption and high brightness. However, there are many technical problems in the mass production and commercialization of OLED urgently needed to be solved.
For example, in the fabrication of OLED, the alignment of electrodes and prevention of short circuits between electrodes is still very important to the patterning and pixel quality of OLED. So far, the shadow mask process is widely applied in the fabrication of OLED to resolve such alignment problems of electrodes on the display panel of OLED. However, because multiple layers of different organic materials and cathode materials have to be deposited, it is difficult to use external shadow masks to accurately align each layer to form patterns on the substrate of panels, especially for the alignment of patterns with high resolution of multiple layers.
On the other hand, OLED with good display quality such as lifetime and reliability, simple processing method, low price, higher resolution, and thinner display panel (i.e. less thickness) is immediately necessary now. Nevertheless, because there are many technical problems still require to be overcome, the resolution and the thickness of OLED still cannot be effectively improved at the same time. Recently, several technologies are proposed to improve the processing of OLED, but obvious improvement on resolution and thickness of OLEDs is still very rare.
For example, Burrowa et al. disclosed a technology to form a multiple intrinsic shadow mask layer having an undercut on the substrate of display panel to accurately align the organic functional mediums and electrodes (e.g. anodes) in U.S. Pat. No. 6,013,538. The intrinsic shadow mask layer proposed by Burrowa et al. is made by multiple materials and complicated process. The cost of materials is high for this multiple shadow mask because many different materials are needed. The yield of this multiple shadow mask process is limited because complicate processing steps are required, too. In U.S. Pat. No. 5,962,970 Yokoi et al. disclosed another method to fabricate panels of organic light emitting devices. Yokoi et al. revealed in U.S. Pat. No. 5,962,970 a method to form a pattern of isolating layer having reverse-trapezoid cross-section to work as an intrinsic shadow mask and a wall to separate cathode materials from anodes for improving the display quality of the panels. However, the thickness (height) and the resolution of the isolating layer having reverse-trapezoid cross-section are limited. The thickness (or height) of isolating layer is required to be high enough (e.g. at least more than 6 xcexcm) to avoid possible short circuits resulted from direct contact of cathode materials and anodes. As cathode formed through deposition, cathode materials will deposit on the protruding part of isolating layer. To avoid direct contact between anode and cathode materials deposited on the side walls of insulating layers (owing to lateral diffusion of cathode materials in evaporative directions), the isolating layer having reverse-trapezoid cross-section should be wide enough to act as shadow walls to separate anode materials from cathode to avoid possible shorts. If the height of isolating layer is too low, the protruding part of the isolating layer will be not wide enough to separate the side-deposited cathode materials from contacting anodes. Thus, the thickness and the width of the isolating layer having reverse-trapezoid cross section cannot be effectively reduced. Therefore the corresponding resolution and the thickness of the panel of the OLED is limited. On the other hand, since the shape of the isolating layer is reverse-trapezoid, the width of the base of the isolating layer is narrower than the width of top. The width of the base of the isolating layer having reverse-trapezoid cross section are required to be wide enough to support the isolating layer and exempt from collapsing of isolating layer. The average minimum width of the isolating layer processed by the method taught in U.S. Pat. No. 5,962,970 is around 15 xcexcm. The average minimum height of the isolating layer processed by the method described in U.S. Pat. No. 5,962,970 is around 6 xcexcm. The corresponding resolution and the thickness of the panel of the OLED is significantly limited.
In 1997, another method for manufacturing organic emitting devices is disclosed in U.S. Pat. No. 5,701,055. Nagayama et al. disclosed a technology to form isolating layers on panel substrate to avoid direct contact between cathode materials and anodes in U.S. Pat. No. 5,701,055. In U.S. Pat. No. 5,701,055, isolating layers having multi-layer T-shaped cross-section or reverse-trapezoid cross-section is formed on the substrate to avoid direct contact between cathode materials and anodes. Thus the isolation between anodes and cathodes of organic light emitting devices can be solved. Nevertheless, the isolating layers having T-shaped cross-section mutilayer disclosed in U.S. Pat. No. 5,701,055 are made by more than two materials. Multiple masks and lithographic processes are required for the formation of isolating layers having T-shaped cross-section in U.S. Pat. No. 5,701,055. The method for forming isolating layers having T-shaped cross-section in U.S. Pat. No. 5,701,055 solved the isolation between anodes and cathodes of OLED. However, the complicate steps of the method for forming isolating layers having T-shaped cross-section in U.S. Pat. No. 5,701,055 cost expensive because many different materials, reagents and complex processes are required. So far, the OLEDs meeting all the requirements such as relatively simple fabricating process, low cost, less material consumption, capability of mass production, high reproducible yield, high resolution and relatively low thickness are not disclosed yet and still in urgently demand now.
The object of the present invention is to provide a surface treatment process for fabricating a panel of an OLED having relatively high resolution and relatively low thickness.
Another object of the present invention is to provide a surface treatment process for preventing possible shorts of a panel of an OLED.
Another object of the present invention is to provide a surface treatment process of a panel of an OLED for facilitating the process, reducing cost and increasing the yield.
Another object of the present invention is to provide a surface treatment process for preventing OLEDs from shorts caused by lateral diffusion and collapse of the surface layers of OLEDs.
The surface treatment process for fabricating a panel of an OLED of the present invention comprising following steps: forming on a substrate a plurality of first electrodes; forming a plurality of ramparts having T-shape cross-section on said substrate and selectively on said first electrodes through coating positive chemically amplified photoresist compositions having photo-acid generators on said substrate, exposing coated substrate to ultraviolet (UV) radiation to form latent patterns, post-exposure surface-treating said photoresist on said substrate in an alkaline atmosphere and developing said photoresist; wherein each rampart protruding from said substrate and having an overhanging portion projecting in a direction parallel to said substrate; depositing organic electroluminescent media to the exposed areas between said ramparts on said substrate; forming a plurality of second electrodes on said organic electroluminescent media on said substrate.
The OLEDs of the present invention comprise: a substrate on which a plurality of first electrodes are formed; a plurality of ramparts having T-shape cross-section formed on said substrate and selectively on said first electrodes through coating positive chemically amplified photoresist compositions having photo-acid generators on said substrate, exposing coated substrate to UV radiation to form latent patterns, post-exposure surface-treating said photoresist on said substrate in an alkaline atmosphere and developing said photoresist; wherein each ramparts protruding from said substrate and having an overhanging portion projecting in a direction to said substrate; an organic function layers which includes at least one organic electroluminescent medium formed on the exposed areas between ramparts; and a plurality of second electrodes formed on organic functional layer.